Portions of North Main Street (Route 28) will be closed Thursday for the funeral for Boston officer and Randolph native Dennis “DJ” Simmonds Jr., who was injured during the 2013 shootout with Boston Marathon bombing suspects Tamerlan and Dzhokhar Tsarnaev. He died unexpectedly on April 10 at age 28.

With Wednesday visiting hours and a Thursday funeral set for decorated Boston police officer and Randolph native Dennis Oliver “DJ” Simmonds Jr., Randolph’s police chief says some of the town’s main routes will be closed and detoured at those times.

“We’re expecting 3,000 to 4,000 (mourners),” Chief William Pace said. “That will have quite an impact on traffic.”

Simmonds drew national praise for his bravery during last April’s police chase and shootout in Watertown with Boston Marathon bombing suspects Tamerlan and Dzhokhar Tsarnaev. He suffered serious head injuries when one of the brothers tossed an explosive close to where he was standing. It took him months to recover.

Simmonds, a Randolph High graduate who lived in Hyde Park, was scheduled to receive the National Association of Police Organization’s “Top Cop Award” from President Barack Obama on May 12. He unexpectedly died from a medical emergency while on duty on April 10. He was 28.

The cause of his death hasn’t been determined. He’d been on the Boston force for six years, and last worked with the department’s youth violence strike force. He received the Boston Police’s top honor earlier this year.

With perhaps thousands of police expected to gather to honor Simmonds, Pace said stretches of North Main Street (Route 28) will be closed from 4 to 8 p.m. Wednesday and again from 9 a.m. to 1 p.m. Thursday.

For Wednesday visiting hours at Cartwright Funeral Home, 419 N. Main St., Pace said the road will be closed between Liberty and West streets. The northbound lanes will be detoured at Pleasant Street onto North Street. Southbound lanes will be re-routed at Liberty Street.

For Thursday’s 11 a.m. funeral at First Baptist Church in Randolph, the northbound lanes of North Main will be closed at West Street, and the southbound lanes at Oak Street.